The present invention relates to a reclining apparatus installed in a seat for a vehicle, and in particular, to a reclining apparatus having a neutral position return function where the backrest which has been reclined forward through the operation by a passenger can be returned and secured to a preset position (within a range of an adjustment of the inclination angle) with a simple operation.
Various types of conventional apparatuses have been proposed as a reclining apparatus installed in a seat for a vehicle. From among these, reclining apparatuses which are mounted in seats in the front row of coupe style vehicles and three door hatchback style vehicles and seats in the second row of minivans and cab wagon style vehicles so that the passengers can get into and leave from the seats in the rear row are put into practice, and many vehicles are equipped with these. Such reclining apparatuses have a neutral position return function which makes it possible for the backrest to recline forward to a great degree and automatically return and be secured to the preset position (neutral position) by simply raising the above described backrest after the completion of getting into and leaving from the seats in the rear row.
Apparatuses such as those described in Japanese Unexamined Patent Publication H2 (1990)-177908, for example, are publicly known as reclining apparatuses having the above described neutral position return function. The apparatus described in this publication adopts a configuration wherein a sector plate 8, in which a sector gear 9 having external cogs is formed, is secured to a rotational bracket 5 on the backrest side, a lock plate 11, in which a lock gear 17 is formed, is secured to a stationary bracket 3 on the seat side with an axis, and a memory plate 20 for preventing the engagement between the sector gear 9 and the lock gear 17 under certain conditions is provided so as to intervene in between. Thus, the above described memory plate 20 works to allow the backrest to return and be secured to the preset neutral position simply by raising the backrest that has been reclined forward.
Meanwhile, as for compact and lightweight reclining apparatuses which can be easily attached to a seat, apparatuses which are referred to as round reclining apparatuses (circular reclining apparatuses) are put into practice. In these round reclining apparatuses, a base plate in approximately disc form and a gear plate in approximately disc form are combined so as to face each other, and a locking mechanism is provided in the internal space across which the two plates face each other so that the two plates rotate relative to each other with a center shaft as a fulcrum, making it possible to be secured at a desired position, or phase.
As a concrete configuration of these round reclining apparatuses, the one described in Japanese Patent No. 3343039, for example, is publicly known. In the apparatus described in this patent, two pegs 12 (corresponding to “protrusions”) are formed so as to protrude from a follower 5 (corresponding to a “lock gear”) in the direction of the axis, in addition to the above described respective components, so that one peg 12 allows the locking mechanism to be held in a released position in a predetermined range while the other peg 12 and a thin plate 14 having a circular orbit P (corresponding to a “guide hole”) with a step, control the release of the lock. That is to say, the seats to which such an apparatus is attached have such a configuration that when the backrest is reclined forward at the time of getting into or leaving from the rear seat of the vehicle, the locking mechanism is maintained in a release position even after the operation of the operation member is released, and the backrest is returned and secured to the front end in the range of the adjustment (the highest raised position where the backrest is raised the most as long as it can be secured) when the backrest that has been reclined forward is raised.
In addition, a reclining apparatus is proposed in Japanese Unexamined Patent Publication H8 (1996)-300990 as a reclining apparatus where a function of returning and being secured to a position within the range of the adjustment is added to the above described round reclining apparatus, and a function (full memory function) of automatically returning to the original position where the angle has been adjusted to the angle before the backrest is reclined forward when the backrest is reclined backward starting from the forward reclined position is provided. The reclining apparatus described in this publication is provided with a ring 11 having a first side plate 8 (a plate in disc form) and a second side plate 9 (a plate in disc form) and a pair of internal cogs 19, with a locking and lock releasing mechanism M between the cogs 12 of the above described ring 11 and the first side plate 8 (a conventional angle adjustment mechanism) and a second mechanism (a full memory mechanism) for locking and lock releasing between the cogs 12 of the above described ring 11 and the second side plate 9, and for storing the adjusted location when working together with a crossing plate. That is to say, the round reclining apparatus according to this publication has a conventional mechanism M for adjusting the reclining angle, and a second mechanism for performing the full memory function, and thus adopts a configuration where the angle adjustment mechanisms in conventional reclining apparatuses are combined so as to be duplicated.